Combined natural wastewater treatment systems for removal of organic matter and phosphorus from polluted streams

Abstract

Natural wastewater treatment (NWT) systems may be a most suitable and economical solution method to ensure a cleaner environment and sustainable production in control of water pollution. Therefore, in this study, a NWT system was designed to reduce existing pollution in over-polluted Kızılca creek (Nigde, Turkey). The combined system consists of a settlement basin (SB), free water surface constructed wetland (FWS-CW) planted with Phragmites communis, and overland flow (OF) system planted with Italian ryegrass, respectively. The system was installed on the edge of the creek in 2014. Over-polluted creek water was treated by passing through the system, and the treated water was discharged into the creek. Total suspended solid (TSS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total phosphorus (TP) parameters were analyzed on samples taken from the inputs and outputs of all stages of the system. During an operating period of about 18 months, it was observed that the pollutant parameters were reduced to a great extent. Despite the high organic loading, it was determined that the treatment system could remove the TSS and the BOD up to 85%, and the TP up to 49%. Average removals were found to be higher in warm weather conditions where vegetation could grow best. Results suggest that the combined NWT systems can be used as a low-cost wastewater treatment alternative to improve the water quality of polluted streams in similar areas.